Polymers with improved toughness and ESCR for large-part blow molding applications
Disclosed herein are ethylene-based polymers having a density greater than 0.945 g/cm 3 , a high load melt index less than 25 g/10 min, a peak molecular weight ranging from 52,000 to 132,000 g/mol, and an environmental stress crack resistance of at least 250 hours. These polymers have the processability of chromium-based resins, but with improved impact strength and stress crack resistance, and can be used in large-part blow molding applications.
1. An ethylene/a-olefin copolymer composition having a density in a range from about 0.95 to about 0.965 g/cm 3 , a high load melt index (HLMI) in a range from about 2 to about 10 g/10 min, a peak molecular weight (Mp) in a range from about 65,000 to about 115,000 g/mol, a Mn in a range from about 30,000 to about 60,000 g/mol, a Mz in a range from about 1,750,000 to about 4,000,000 g/mol, and a ratio of Mw/Mn in a range from about 7 to about 15.
2. An article comprising the copolymer composition of claim 1 .
3. The copolymer composition of claim 1 , wherein the copolymer composition has:
an environmental stress crack resistance (ESCR) of at least 500 hours;
a Tensile Impact in a range from about 450 to about 1000 kJ/m 2 ; and
a Charpy Impact in a range from about 25 to about 75 kJ/m 2 .
4. The copolymer composition of claim 1 , wherein the copolymer composition has:
an environmental stress crack resistance (ESCR) of at least 1000 hours;
a Tensile Impact in a range from about 500 to about 1000 kJ/m 2 ; and
a Charpy Impact in a range from about 30 to about 70 kJ/m 2 .
5. The copolymer composition of claim 1 , wherein the copolymer composition is an ethylene/1-butene copolymer composition, an ethylene/1-hexene copolymer composition, or an ethylene/1-octene copolymer composition.
6. A blow molded article comprising the copolymer composition of claim 5 .
7. The copolymer composition of claim 1 , wherein the copolymer composition has a viscosity at 100 sec −1 in a range from about 2000 to about 3800 Pa-sec.
8. The copolymer composition of claim 1 , wherein the copolymer composition has:
a bimodal molecular weight distribution; and
a weight-average molecular weight in a range from about 325,000 to about 575,000 g/mol.
9. The copolymer composition of claim 8 , wherein the copolymer composition is an ethylene/1-butene copolymer composition, an ethylene/1-hexene copolymer composition, or an ethylene/1-octene copolymer composition having a density in a range from about 0.952 to about 0.962 g/cm 3 .
10. A polymerization process comprising:
contacting a catalyst composition with ethylene and an optional olefin comonomer in a polymerization reactor system under polymerization conditions to produce an ethylene polymer composition; wherein the ethylene polymer composition is characterized by:
a density of greater than or equal to about 0.945 g/cm 3 , a high load melt index (HLMI) in a range from about 2 to about 20 g/10 min, a viscosity at 100 sec −1 in a range from about 2000 to about 4000 Pa-sec, a weight-average molecular weight (Mw) in a range from about 275,000 to about 800,000 g/mol, a number-average molecular weight (Mn) in a range from about 30,000 to about 60,000 g/mol, and a ratio of Mw/Mn in a range from about 5 to about 22.
11. The process of claim 10 , wherein the polymerization reactor system comprises a slurry reactor, a gas-phase reactor, a solution reactor, or a combination thereof.
12. The process of claim 10 , wherein the polymerization reactor system comprises a loop slurry reactor.
13. The process of claim 10 , wherein the polymerization reactor system comprises one or two reactors.
14. The process of claim 10 , wherein the catalyst composition is contacted with ethylene and an olefin comonomer comprising a C 3 -C 10 α-olefin.
15. The process of claim 10 , wherein the catalyst composition comprises two metallocene compounds, an activator, and an optional co-catalyst.